The two-year randomised clinical trial is the largest to study the effect of B vitamins on mild cognitive impairment, and one of the first disease-modifying trials in the Alzheimer's field to show positive results in people.

Around 1 in 6 elderly people over the age of 70 has mild cognitive impairment, experiencing problems with memory, language, or other mental functions, but not to a degree that interferes with daily life. Around half of people with mild cognitive impairment go on to develop dementia -- mainly Alzheimer's disease -- within five years of diagnosis.

Certain B vitamins -- folic acid, vitamin B₆ and vitamin B₁₂ -- are known to control levels of the amino acid homocysteine in the blood, and high levels of homocysteine are associated with an increased risk of Alzheimer's.

So the Oxford team set out to see whether supplements of the B vitamins that lower homocysteine could slow the higher rate of brain shrinkage, or atrophy, observed in mild cognitive impairment or Alzheimer's.

The study followed 168 volunteers aged 70 or over with mild memory problems, half of whom took high dose B vitamin tablets for two years and the other half a placebo tablet. The researchers assessed disease progression in this group by using MRI scans to measure the brain atrophy rate over a two-year period. The findings are published in the journal PLoS ONE.

The team found that on average the brains of those taking the folic acid, vitamin B₆ and B₁₂ treatment shrank at a rate of 0.76% a year, while those in the placebo group had a mean brain shrinkage rate of 1.08%. People with the highest levels of homocysteine benefited most, showing atrophy rates on treatment that were half of those on placebo.

Along with rate of brain shrinkage, the team from the Oxford Project to Investigate Memory and Ageing (OPTIMA) also monitored cognitive test scores, revealing that those with the slowest rate of shrinkage scored more strongly.

The team suggests that, since the rate of brain atrophy is known to be more rapid in those with mild cognitive impairment who go on to develop Alzheimer's, it is possible that the vitamin treatment could slow down the development of the disease. Clinical trials to test this should now be carried out, they add.

'It is our hope that this simple and safe treatment will delay the development of Alzheimer's disease in many people who suffer from mild memory problems,' said Professor David Smith of the Department of Pharmacology at Oxford University, a co-leader of the trial. 'Today there are about 1.5 million elderly in UK, 5 million in USA and 14 million in Europe with such memory problems.

'These are immensely promising results but we do need to do more trials to conclude whether these particular B vitamins can slow or prevent development of Alzheimer's. So I wouldn't yet recommend that anyone getting a bit older and beginning to be worried about memory lapses should rush out and buy vitamin B supplements without seeing a doctor,' he said.

Rebecca Wood, Chief Executive of the Alzheimer's Research Trust, which co-funded the study, said: 'These are very important results, with B vitamins now showing a prospect of protecting some people from Alzheimer's in old age. The strong findings must inspire an expanded trial to follow people expected to develop Alzheimer's, and we hope for further success.

'We desperately need to support research into dementia, to help avoid the massive increases of people living with the condition as the population ages. Research is the only answer to what remains the greatest medical challenge of our time.'

Professor Chris Kennard, chair of the Medical Research Council's Neurosciences and Mental Health Board which co-funded the study, said: 'This MRC-funded trial brings us a step closer to unravelling the complex neurobiology of ageing and cognitive decline, which holds the key to the development of future treatments for conditions like Alzheimer's disease. The findings are very encouraging and we look forward to further research that is needed in order to test whether B vitamins can be recommended as a suitable treatment.'

Note: If no author is given, the source is cited instead.

• Healthy Aging
• Alzheimer's Research
• Vitamin B

• Alzheimer's
• Dementia
• Intelligence

• B vitamins
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